Japanese Unexamined Patent Application Publication No. 2011-100998 (hereinafter referred to as Patent Document 1) discloses a technique that is of interest to the present invention. In particular, FIGS. 1, 3A, and 3B in Patent Document 1 show a case, including a concave body and a lid, for electric double-layer capacitors. The case is made of resin and holds an external terminal member embedded therein. FIG. 5 shows a case 2 in cross section. The case 2 is one obtained by generalizing the above structure, serves as an insulating section, and holds an external terminal member 1 embedded therein.
As illustrated in FIG. 5, an electronic component 3 including the external terminal member 1 and the case 2 is mounted on a mounting substrate 4 in such a way that solder 7 is provided between a conductive land 6 placed on the mounting substrate 4 and an exposed portion 5 of the external terminal member 1 that is directed outward and reflowing is then performed. In this operation, the solder 7 is melted and protrudes outside the exposed portion 5 of the external terminal member 1 to spread along the lower surface of the case 2 as illustrated in FIG. 5. The contact of the case 2 with the high-temperature melted solder 7 may possibly cause such a failure that the case 2 is partly melted or a crack 8 is formed in the case 2.
In the electronic component 3, in which the case 2 contains a capacitor element and an organic electrolyte solution and the entry of water from outside is strictly inhibited like, for example, an electric double-layer capacitor containing an organic electrolyte solution, the presence of the crack 8 may possibly cause a problem such as a reduction in dielectric strength.